DESCRIPTION: Pedestrian-motor vehicle collisions account for over 6% of all occupational fatalities. Perceptual interventions to reduce these accidents have focused primarily on vision. Auditory methods have received less research attention. However, given the high demands on the visual attention of both pedestrian workers and vehicle operators, auditory warning might be a fruitful avenue for the reduction of traumatic injury to pedestrian workers who interact with motor vehicles. Recent research on the perception of auditory looming has shown that listeners tend to underestimate the amount of time it will take for an approaching sound source to reach them. The perceptual bias effectively signals that the source is closer than actual and thus, gives the listener more time than expected to avoid collision (the margin of safety effect). However, there are two caveats to these findings that are important with regard to the reduction of worker fatality and traumatic injury. First, much of the research on auditory looming has been done with source velocities that are far below those typical of motor vehicles. Second, there is emerging evidence to suggest that the perceptual margin of safety for auditory looming is greater for tones than for the broadband noise that is typically emitted by motor vehicles. The objectives of this research are to identify the specific acoustic conditions that maximize the perceptual bias to hear looming sound sources as closer than actual, and the specific conditions that allow the earliest detection of looming auditory motion. This information can then be used to enhance pedestrian safety in a cost effective manner by taking advantage of auditory perceptual biases. For example, if tonal sounds are found to increase the looming bias, then making approaching vehicles produce subtle tones with a temporary a pavement treatment should increase the margin of worker safety. Psychoacoustic experiments will be carried out that examine the perception of auditory looming and the initial detection of egocentric auditory motion. Specifically, the characteristics of source velocity and spectrum (tones vs. noise) will be investigated in order to bring to the workplace the largest possible "margin of safety" in detecting and perceiving looming motor vehicles. By capitalizing on perceptual biases in auditory perception, the results of this work will provide specific, cost effective recommendations for reducing a leading cause of traumatic occupational injury and death.